The invention relates to a lighting or signaling device for a vehicle.
A headlight for a vehicle is known, comprising a casing made of plastic and a lamp holder fixed to the back wall of the casing. Producing the casing from plastic makes the device inexpensive to manufacture. On the other hand, certain problems may be encountered: under the heat given off by the lamp, deformation or softening of the back wall may occur, which may lead to an alteration in the positioning of the lamp with respect to the reflector, such that the beam no longer appropriately fulfils its function.
An object of the invention is to propose a lighting or signaling device with a plastic back wall making it possible to circumvent the drawbacks relating to the heat given off by the lamp.
With a view to achieving this object, a lighting or signaling device for a vehicle is proposed, according to the invention, comprising a plastic back wall and a lamp holder fixed to the back wall, the device further including a metal plate fixed to the back wall extending from one side of the back wall turned towards the lamp, the lamp holder being supported on the metal plate along an axial direction of the lamp and including at least one metal element in contact with the metal plate.
Thus, the metal plate reinforces and stiffens the back wall. The mechanical resistance of the wall, even under the effect of the heat, is thus increased. Moreover, the metal plate receives some of the heat from the back wall, or, what is more, even receives the heat from the lamp directly, and dissipates it into the air surrounding the plate (by forming a radiator) which keeps the back wall at a relatively low temperature. Thus reinforced, and heated less, the back wall is less deformed. Hence the positioning of the lamp with respect to the reflector is preserved, so that the correct beam is obtained.
The metal plate forms a thermal screen between the lamp and the back wall. The radiation received by the back wall is thus reduced, so that its temperature remains only slightly elevated. The metal plate also defines the position of the lamp. Having regard to the rigidity of the metal plate, this positioning is particularly accurate. The heat from the lamp holder is thus transmitted to the plate. This further contributes to reducing the temperature of the back wall.
Advantageously, the metal plate features at least one fold.
This fold reinforces the rigidity of the metal plate.
Advantageously, the metal plate features at least one edge region extending at a distance from all the other pieces of the device.
This region, forming a radiator, makes it possible to cool the metal plate better.
Advantageously, the device includes limit-stop means for countering the rotation of the metal plate with respect to the back wall in at least one direction.
Advantageously, either one of the wall and the metal plate includes at least one relief and the other of the wall and the metal plate features at least one orifice for retaining the relief.
Advantageously, the device includes two reliefs and two orifices, at least one of the reliefs being able to penetrate into a single one of the orifices.
Thus an indexing means is obtained for fitting the metal plate onto the back wall in the correct position.
Advantageously, the or each orifice is defined by at least one flexible prong.
This prong makes it possible to increase the tolerances allowing suitable retention of the relief in the orifice.
Advantageously, the device includes bayonet-type means for fixing the lamp holder to the plate.
Advantageously, the device is configured in such a way that the bayonet fittings come to bear on the metal plate along an axial direction of the lamp.
Advantageously, the device features ramps able to be traveled by the bayonet fittings while the lamp holder is rotated in order to bring the bayonet fittings to bear on the metal plate.
Assembly is thus facilitated. Moreover, the absence of ramps associated with the other direction of rotation forms an indexing means for the correct fitting of the lamp holder onto the device.
Advantageously, the device includes a casing, glazing, an intermediate piece linking the glazing to the casing and a screen extending forwards from an upper region of the casing towards the glazing.
Thus, the screen receives the rising hot air. A fraction of the heat is thus picked up by the screen and not by the intermediate piece. Thus the risk of deforming the latter is reduced. As for the screen, it can be deformed to a large extent without impairing the operation of the device.
Advantageously, the device includes a reflector mounted so as to be moveable with respect to the casing, the lamp being fixed rigidly to the casing.
Advantageously, the device includes a casing comprising the back wall, a reflector and a cradle linking the reflector to the casing and featuring an aperture in the upper part.
Thus, the aperture corresponds to the region of the cradle which otherwise would be most exposed to the heat. Moreover, the aperture allows a certain amount of dilation of the cradle. The thermal behavior of the cradle is thus enhanced, which promotes correct positioning of the reflector with respect to the lamp. Moreover, this aperture reduces the volume of the cradle and gives it an overall size allowing certain kinematics for fitting the cradle with respect to the reflector, such as assembly by pivoting, for example, which otherwise would be prohibited. Moreover, this aperture achieves an indexing effect for the correct fitting of the cradle into the device. Finally, it gives rise to a reduction in material. Thus results in a saving in weight and in cost, which is all the more important since high-grade plastics, which have good heat resistance but are often expensive, are usually used for this type of piece.
Advantageously, what is involved is a headlight.
Advantageously, what is involved is a fog lamp.
Other characteristics and advantages of the invention will emerge further from the following description of a preferred embodiment and of variants which are given by way of non-limiting examples.